The head of Libya's parliament has confirmed businessman Ahmed Maetig as the country's new prime minister, according to a decree he signed a day after the parliament’s deputy speaker declared Maetig's election invalid.

"Ahmed Maetig was appointed head of the transitional government, and asked to form his cabinet and present it to the parliament, the General National Congress, for a confidence vote within 15 days," said the text of a decree signed on Monday by speaker Nouri Abu Sahmain.

Parliament elected Maetig on Sunday after chaotic voting but First Deputy Speaker Ezzedin al-Awami initially said the businessman had failed to obtain the necessary quorum.

Maetig had secured 113 votes in the GNC on Sunday night, but needed 120 to be declared the country's new prime minister in accordance with the constitution, said the government's official website.

After the initial vote count, GNC official Salah al-Makhzum said Maetig had in fact clinched 121 votes in the 185-seat interim parliament, apparently after a recount, and beat challenger Omar al-Hassi, a university professor.

Some deputies denounced the recount, which they said took place after the session had officially closed.

Political turmoil

The divisions in the assembly highlighted growing political turmoil in Libya, where the government and parliament are unable to assert their authority in a country awash with arms and fighters from the 2011 toppling of Muammar Gaddafi.

Thinni's short-lived tenure followed that of Ali Zeidan who fled the country after he was fired by deputies over his failure to stop attempts by rebels in the volatile east to sell oil independently of Tripoli's government.

Since the civil war that ended Gaddafi's one-man rule, Libya's nascent democracy has struggled, with its parliament paralysed by rivalries and brigades of heavily armed former rebels challenging the new authorities.

The country's fledgling army faces challenges from unruly ex-rebels, tribal groups and fighters.